AccessType Aglen albers_conical_equal_area_to_proj args_string average_water_column_pressure axis_type_from_string AxisType azimuthal_equidistant_to_proj backend_to_string bedrock_surface_temperature blatter_xy_exact blatter_xy_source blatter_xz_cfbc_base blatter_xz_cfbc_exact blatter_xz_cfbc_source blatter_xz_cfbc_surface blatter_xz_exact blatter_xz_halfar_exact blatter_xz_halfar_source blatter_xz_halfar_source_base blatter_xz_halfar_source_lateral blatter_xz_halfar_source_surface blatter_xz_source blatter_xz_source_bed blatter_xz_source_surface blatter_xz_vanderveen_beta blatter_xz_vanderveen_exact blatter_xz_vanderveen_source_lateral blatter_xz_vanderveen_source_surface blatter_xz_vanderveen_thickness Box c1 c2 calendar calendar_from_file cf_to_proj check_c_call check_consistency_epsg check_forcing_duration check_input check_petsc_call choose_backend clear_fftw_array clip combine common_flags compute_area compute_cell_areas compute_coordinates compute_corrective_velocity compute_grounded_cell_fraction compute_horizontal_grid_size compute_horizontal_spacing compute_interface_velocity compute_lat_bounds compute_latitude compute_lon_bounds compute_lon_lat compute_lon_lat_bounds compute_longitude compute_node_types compute_strain_heating_errors computeSurfaceVelocityErrors config_from_options ConfigSettingFlag contains_epsg context_from_options convert_vec convert_vec copy_fftw_array count_CFL_violations create_backend create_restriction criticalW diag_metadata DiagnosticList Direction dx_estimate dx_min dy_estimate dy_min effective_change end_time ends_with enthalpy_from_temperature_cold epsg_to_cf exactFG exactP exactP_list F F fftfreq filename_add_suffix find_json_value fletcher64 floating_ice_sheet_area_fraction_name funcP g generate_mound_topography generate_trough_topography get_ get_all_arrays get_all_values get_proj_parameters get_real_part get_shared_ get_time get_value getsb getW GlobalMax GlobalMax GlobalMax GlobalMin GlobalMin GlobalReduce GlobalReduce GlobalSum GlobalSum GlobalSum GlobalSum GlobalSum Grid_FromFile grid_name grid_subset grid_transpose grid_z grounded_area_fraction grounded_ice_sheet_area_fraction_name h0 handle_fatal_errors ice_area ice_area_floating ice_area_grounded ice_bottom_surface ice_flow_rate_across_grounding_line ice_volume ice_volume_not_displacing_seawater IceModelTerminationReason increment_date init_interpolation_indexes init_step initialconditionW InitializationType integration_weights integration_weights InterpolationType intersect_ab intersect_ac intersect_bc invalid is_increasing join join_impl k label_components_impl lambert_azimuthal_equal_area_to_proj lambert_conformal_conic_to_proj lambert_cylindrical_equal_area_to_proj land_ice_area_fraction_name lapse_rate_correction latitude_longitude_to_proj limit_advective_flux limit_diffusive_flux logger_from_options LoggerLevel LonLat m0 make_nonnegative_preserving MaskValue max_timestep_cfl_2d max_timestep_cfl_3d max_timestep_diffusivity member mercator_to_proj Metadata nc_type_to_pism_type netcdf_version NodeType operator* operator< operator== operator> orthographic_to_proj p3 p4 pack_json_array parse_date parse_epsg parse_integer parse_integer_list parse_number parse_number_list part_grid_threshold_thickness pism_is_valid_calendar_name pism_type_to_nc_type pism_yac_error_handler polar_stereographic_to_proj print_checksum print_config print_diagnostics print_diagnostics_json print_unused_parameters print_vector print_vector printf process_extra_shortcuts process_input_options process_ts_shortcuts psteady R1 reference_date reference_date_from_file remove_narrow_tongues replace_character report_range reportErrors reporting_max_timestep restrict_data rhoi rhow rotated_latitude_longitude_to_proj same sea_level_rise_potential secondInvariant_2D set_config_from_options set_flag_from_option set_integer_from_option set_join set_keyword_from_option set_no_model_strip set_no_model_yield_stress set_number_from_option set_parameter_from_options set_real_part set_split set_string_from_option set_value setInitStateF setup_level show_usage show_usage_check_req_opts SNESScalarProblem SNESVectorProblem special_parameter SperA split square start_time step step stereographic_to_proj string_is_false string_is_true string_strip string_to_backend subset_start_and_count TEMPORARY_STRING_LENGTH timestamp total_grounding_line_flux transverse_mercator_to_proj triangle_area ts_diag_metadata TSDiagnosticList UNOType unpack_json_array upwind username_prefix v0 validate_format_string vector_max vector_min version vertical_perspective_to_proj volume_flow_rate_from_land_to_water wall_clock_hours warn_about_missing weights_piecewise_constant weights_piecewise_linear Wr write write_mapping write_run_stats

label_components_impl() template<typename T > void pism::label_components_impl ( const T &  input, bool  mark_isolated_patches, array::Scalar1 &  output  ) Labels connected components in parallel, using a custom definition of "foreground" and "attached" grid cells. Note that connected_components::details::label() below is a template function: this is why we have to include the implementation here. The type T has to implement is_foreground(row, col) and is_attached(row, col). Here's the idea: Identify connected components in each sub-domain. "Update ghosts" of output, then iterate over sub-domain edges to identify connections between patches in sub-domains that make up connected components spanning multiple sub-domains. This defines a graph: each patch on a sub-domain is a node, two nodes are connected by an edge if and only if they "touch". Gather graph description on all sub-domains that have at least one patch. Use breadth-first search to traverse this graph and compute final labels. Apply final labels. This method communicates ghosts (once), number of graph edges per sub-domain (once) and then all graph edges (once, only to sub-domains that have at least one patch). Graph traversal is done "redundantly", i.e. each participating sub-domain traverses the whole graph even if it contains one isolated node. This is needed to ensure that resulting labels use consecutive numbers. (Consecutive labels are useful for indexing elsewhere in the code). We /could/ gather graph information on one MPI processor, traverse the graph to compute final labels, then scatter final labels. It is not clear if this would be better, though. The current implementation uses MPI_Allgather() to gather number of graph edges per subdomain (send 4 bytes, receive 4 bytes per subdomain). MPI_Allgatherv() to gather edges to all participating subdomains (send 8 bytes per local edge, receive 8-16 bytes per edge). The alternative implementation would use MPI_Gather() to gather number of graph edges per sub-domain to one of sub-domains. (each sub-domain sends 4 bytes, one sub-domain receives 4 bytes per sub-domain). MPI_Gatherv() to gather edges from all participating sub-domains. (All sub-domains send 8 bytes per local edge, one sub-domain receives 8 bytes per edge in the whole graph.) MPI_Bcast() to scatter the mapping from old labels to new labels (8 bytes per local sub-domain). TO DO: run benchmarks! Definition at line 95 of file label_components_impl.hh. References pism::details::final_labels(), pism::details::first_label(), pism::array::Array::grid(), and pism::details::relabel(). Referenced by pism::connected_components::label(), and pism::connected_components::label_isolated().